Communication system, communication apparatus and communication method as well as program

ABSTRACT

A communication apparatus is provided and including a carrier wave generator configured to generate a first electromagnetic wave; a modulator configured to modulate the first electromagnetic wave for transmitting a first message to a first communication device; a load modulator configured to modulate a second electromagnetic wave generated by the first communication device for transmitting a second message to the first communication device; a controller configured to control the communication apparatus to: transmit the first message when the second electromagnetic wave is not detected and, transmit the second message when the second electromagnetic wave is detected. A communication method is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/630,822, filed Feb. 25, 2015, which is a continuation ofU.S. patent application Ser. No. 13/527,093, filed Jun. 19, 2012, nowU.S. Pat. No. 8,996,731, issued Mar. 31, 2015, which is a continuationof U.S. patent application Ser. No. 10/557,272 filed on Feb. 24, 2006,now U.S. Pat. No. 8,244,917, issued Aug. 14, 2012, which is a U.S.national phase of International Application Serial No. PCT/JP04/008169filed Jun. 4, 2004, which claims priority to Japanese Application2003-162427 filed Jun. 6, 2003, the entire contents of each of which arehereby incorporated by reference herein.

BACKGROUND

The present disclosure relates to a communication system, acommunication apparatus, and a communication method as well as to aprogram, and in particular, to a communication system, a communicationapparatus, and a communication method as well as to a program capable ofacquiring the advantages of a plurality of communication protocols.

Recently, wireless communications, for example, Wireless Local AreaNetwork (WLAN), Bluetooth (registered trademark) (hereinafter,appropriately abbreviated as BT communication), an integrated circuit(IC) card system, and the like have become a focus of attention.

In, for example, the IC card system among these wireless communications,a reader/writer generates an electromagnetic wave to thereby form aso-called radio frequency (RF) field (magnetic field). Then, when an ICcard is brought into vicinity of the reader/writer, the IC card issupplied with power by electromagnetic induction as well as data istransmitted between the IC card and the reader/writer.

There are specifications called a type A and a type B as thespecification of the IC card embodied at present.

The type A is employed as MIFARE system of Philips, and data istransmitted from a reader/writer to an IC card by encoding data byMiller, and data is transmitted from the IC card to the reader/writer byencoding data by Manchester. Further, the type A employs 106 kilobyteper second (kbps) as a data transmission rate.

In the type B, data is transmitted from a reader/writer to an IC card byencoding data by NRZ, and data is transmitted from the IC card to thereader/writer by encoding data by NRZ-L. Further, the type B employs 106kbps as a data transmission rate.

Further, as the IC card, there is proposed a system for selecting acommunication protocol to be used from a plurality of communicationprotocols and executing a communication by the selected communicationprotocol (refer to, for example, Japanese Unexamined Patent ApplicationPublication No. 06-276249).

Incidentally, in the IC card system disclosed in Japanese UnexaminedPatent Application Publication No. 06-276249, although a communicationcan be executed by a plurality of communication protocols, after acommunication protocol to be used is selected, the communication isexecuted by the selected communication protocol. Accordingly, after thecommunication protocol is selected, the communication cannot be executedby the other communication protocols.

In contrast, a communication protocol, which executes a communication byspecifying, for example, an IC card as a communication opponent, isemployed in, for example, the IC card system. Further, a communicationprotocol, which can transmit data at a speed higher than that of thecurrent IC card system, is employed in, for example, BT communication.Accordingly, if a communication protocol can be switched to acommunication protocol for executing BT communication in, for example,the IC card system after an IC card as a communication opponent isspecified, data can be transmitted at high speed. More specifically, inthis case, the advantages of a plurality of communication protocols canbe obtained in that a communication opponent can be specified by thecommunication protocol employed in the IC card system, and further datacan be transmitted at high speed by the communication protocol forexecuting BT communication.

SUMMARY

The present system, method, apparatus, and program are made in view ofthe above circumstances and can execute a communication capable ofacquiring the advantages of a plurality of communication protocols.

A communication system according to an embodiment has a plurality ofcommunication apparatuses is characterized in that each of the pluralityof communication apparatuses comprises a first communication mean forexecuting a communication between each communication apparatus and othercommunication apparatus by a first communication protocol, an exchangemeans for exchanging communication information necessary to acommunication executed by a second communication protocol included inthe communication protocols available by the other communicationapparatus between the communication apparatus and the othercommunication apparatus by the communication executed by the firstcommunication protocol, a switching means for switching thecommunication between each communication apparatus and the othercommunication apparatus from the communication executed by the firstcommunication protocol to the communication executed by the secondcommunication protocol, and a second communication mean for executingthe communication by the second communication protocol between eachcommunication apparatus and the other communication mean based on thecommunication information exchanged by the exchange means.

A communication apparatus according to an embodiment is characterized bycomprising a first communication mean for executing a communicationbetween the communication apparatus and the other communicationapparatus by a first communication protocol, an acquisition means foracquiring the information of a communication protocol available by theother communication apparatus through the communication executed by thefirst communication protocol, an exchange means for exchangingcommunication information necessary to a communication executed using asecond communication protocol included in the communication protocolavailable by the other communication apparatus between eachcommunication apparatus and the other communication apparatus by thecommunication executed using the first communication protocol, aswitching means for switching the communication between thecommunication apparatus and the other communication apparatus from thecommunication executed by the first communication protocol to thecommunication executed using the second communication protocol, and asecond communication mean for executing the communication by the secondcommunication protocol between the communication apparatus and the othercommunication apparatus based on the communication information exchangedby the exchange means.

A communication method according to an embodiment is characterized bycomprising a first communication step of executing a communicationbetween a communication apparatus and other communication apparatus by afirst communication protocol, an acquisition step of acquiring theinformation of a communication protocol available by the othercommunication apparatus by the communication executed by the firstcommunication protocol, an exchange step of exchanging communicationinformation necessary to a communication executed by a secondcommunication protocol included in the communication protocols availableby the other communication apparatus between the communication apparatusand the other communication apparatus by the communication executed bythe first communication protocol, a switching step of switching thecommunication between the communication apparatus and the othercommunication apparatus from the communication executed by the firstcommunication protocol to the communication executed by the secondcommunication protocol, and a second communication step of executing thecommunication by the second communication protocol between thecommunication apparatus and the other communication apparatus based onthe communication information exchanged at the exchange step.

A program according to an embodiment is characterized by comprising afirst communication step of executing a communication between acommunication apparatus and other communication apparatus by a firstcommunication protocol, an acquisition step of acquiring the informationof a communication protocol available by the other communicationapparatus by the communication executed by the first communicationprotocol, an exchange step of exchanging communication informationnecessary to a communication executed by a second communication protocolincluded in the communication protocols available by the othercommunication apparatus between the communication apparatus and theother communication apparatus by the communication executed by the firstcommunication protocol, a switching step of switching the communicationbetween the communication apparatus and the other communicationapparatus from the communication executed by the first communicationprotocol to the communication executed by the second communicationprotocol, and a second communication step of executing the communicationby the second communication protocol between the communication apparatusand the other communication apparatus based on the communicationinformation exchanged at the exchange step.

In an embodiment, the communication is executed between thecommunication apparatus and the other communication apparatus by thefirst communication protocol, thereby the information of thecommunication protocol available by the other communication apparatus isacquired by the communication executed by the first communicationprotocol. Further, the communication information necessary to thecommunication executed by the second communication protocol included inthe communication protocols available by the other communicationapparatus is exchanged between the communication apparatus and the othercommunication apparatus by the communication executed by the firstcommunication protocol. Then, the communication between thecommunication apparatus and the other communication apparatus isswitched from the communication executed by the first communicationprotocol to the communication executed by the second communicationprotocol, thereby the communication by the second communication protocolis executed based on the communication information.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view showing an example of an arrangement of an embodimentof a communication system.

FIG. 2 is a view explaining a passive mode.

FIG. 3 is a view explaining an active mode.

FIG. 4 is a block diagram showing an example of an arrangement of aportion of communication apparatuses 1 to 3 for executing a NFCcommunication.

FIG. 5 is a view showing a corresponding relation between thecommunication protocols of the communication apparatuses 1 to 3 and anOSI hierarchy model.

FIG. 6 is a view showing a format of NFCIP-DL PDU.

FIG. 7 is a view showing a format of an NFCIP-DL header.

FIG. 8 is a view showing a format of Data of AVAILABLE_MEDIA Request.

FIG. 9 is a view showing a format of Data of AVAILABLE_MEDIA Response.

FIG. 10 is a view showing a format of Data of MEDIA_HANDOVER Request.

FIG. 11 is a view showing a format of Data of MEDIA_HANDOVER Response.

FIG. 12 is a view showing a communication phase by NFCIP-DL.

FIG. 13 is a flowchart explaining processing executed by an initiator.

FIG. 14 is a flowchart explaining processing executed by a target.

FIG. 15 is a block diagram of examples of functional arrangements of thecommunication apparatuses 1 and 2.

FIG. 16 is a flowchart explaining processing executed by thecommunication apparatuses 1 and 2.

FIG. 17 is a block diagram showing an example of an arrangement of anembodiment of a computer.

DETAILED DESCRIPTION

Embodiments will be described below in detail with reference to thedrawings.

FIG. 1 shows an example of an arrangement of a communication system towhich the present embodiment is applied (system is composed of aplurality of apparatuses coupled with each other logically, and it doesnot matter whether or not the apparatuses having respective arrangementsare accommodated in the same cabinet).

In FIG. 1, the communication system is composed of three communicationapparatuses 1, 2, and 3. Each of the communication apparatuses 1, 2, and3 can execute a communication by a plurality of protocols.

Note that communication apparatuses constituting the communicationsystem are not limited to the communication apparatuses 1, 2, and 3, andthe communication system may be composed of two or four or morecommunication apparatuses.

It is needless to say that the communication system shown in FIG. 1 canbe employed as an IC card system in which at least one of thecommunication apparatuses 1, 2, and 3 is arranged as a reader/writer andat least one of the other communication apparatuses 1, 2, and 3 isarranged as an IC card. Further, the communication system may employ therespective communication apparatuses 1, 2, and 3 as mobile terminalshaving a communication function such as a personal digital assistant(PDA), personal computer (PC), mobile phone, wrist watch, pen, and thelike. That is, the communication apparatuses 1, 2, and 3 are not limitedto the IC card, the reader/writer, and the like of the IC card system.Further, the communication system can be arranged so as to include, forexample, an IC card and a reader/writer constituting a conventional ICcard system, in addition to the communication apparatuses 1, 2, and 3.

In this case, however, each of the communication apparatuses 1, 2, and 3has a function for executing a wireless communication, and a pluralityof communication protocols include Near Field Communication (NFC).

NFC is a communication protocol for a near field communication executedby electromagnetic induction using a single frequency carrier wave, and,for example, 13.56 MHz and the like of an Industrial Scientific Medical(ISM) is employed as the frequency of the carrier wave.

The near field communication means a communication which is possibleeven if a distance between apparatuses communicating with each other iswithin several tens of centimeters and includes a communication executedby apparatuses whose cabinets are in contact with each other.

In NFC, a communication can be executed by two communication modes. Thetwo communication modes include a passive mode and an active mode. Whenan attention is paid to, for example, a communication between thecommunication apparatuses 1 and 2 of the communication apparatuses 1, 2,and 3, in the passive mode, one of the communication apparatuses 1 and2, for example, the communication apparatus 1 transmits data to thecommunication apparatus 2 as the other communication apparatus bymodulating (a carrier wave corresponding to) the electromagnetic wavegenerated by the communication apparatus 1 likewise the IC card systemdescribed above. The communication apparatus 2 transmits data to thecommunication apparatus 1 by load modulating (the carrier wavecorresponding to) the electromagnetic wave generated by thecommunication apparatus 1.

In contrast, in the active mode, any of the communication apparatuses 1and 2 transmits data by modulating (a carrier wave corresponding to) theelectromagnetic wave generated by it.

When the near filed communication is executed by electromagneticinduction, an apparatus, which begins a communication by outputting anelectromagnetic wave first, that is, which takes the initiative of thecommunication, is called an initiator. The initiator executes the nearfield communication by transmitting a command (request) to acommunication opponent, and the communication opponent returns aresponse to the command, and the communication opponent which returnsthe response to the command from the initiator is called a target.

When it is supposed, for example, that the communication apparatus 1begins to output an electromagnetic wave and to communicate with thecommunication apparatus 2, the communication apparatus 2 acts as thetarget and the communication apparatus 2 acts as the target as shown inFIGS. 2 and 3.

As shown in FIG. 2, in the passive mode, the communication apparatus 1as the initiator transmits data to the communication apparatus 2 as thetarget by continuously outputting an electromagnetic wave and modulatingthe electromagnetic wave output thereby. Then, the communicationapparatus 2 transmits data to the communication apparatus 1 by loadmodulating the electromagnetic wave output by the communicationapparatus 1 as the initiator.

In contrast, as shown in FIG. 3, when the communication apparatus 1 asthe initiator transmits data, it transmits the data to the communicationapparatus 2 as the target by beginning to output an electromagnetic waveby itself and modulating it. After the transmission of the data isfinished, the communication apparatus 1 stops outputting theelectromagnetic wave. When the communication apparatus 2 as the targettransmits data, it also transmits the data to the communicationapparatus 2 as the target by beginning to output an electromagnetic waveby itself and modulating it. After the transmission of the data isfinished, the communication apparatus 2 stops outputting theelectromagnetic wave.

Next, FIG. 4 shows an example of an arrangement of a portion, whichexecutes an NFC communication, of the communication apparatus 1 inFIG. 1. Note that since portions, which execute the NFC communication,of the other communication apparatuses 2 and 3 of FIG. 1 are arrangedsimilarly to the communication apparatus 1 of FIG. 4, the explanation ofthem is omitted.

An antenna 11 constitutes a closed loop coil and outputs anelectromagnetic wave by changing a current flowing in the coil. Further,a current flows in the antenna 11 in such a manner that magnetic fluxpassing through the coil as the antenna 11 changes.

A receiver 12 receives the current flowing in the antenna 11, tunes anddetects the current, and outputs it to a demodulator 13. The demodulator13 demodulates a signal supplied from the receiver 12 and supplies it toa decoder 14. The decoder 14 decodes, for example, Manchester Code asthe signal supplied from the demodulator 13 and supplies data obtainedas a result of decode to a data processor 15.

The data processor 15 executes predetermined processing based on thedata supplied from the decoder 14. Further, the data processor 15supplies data, which is to be transmitted to other apparatus, to anencoder 16.

The encoder 16 encodes the data supplied from the data processor 15 to,for example, Manchester Code and the like and supplies it to a selector17. The selector 17 selects any one of a modulator 19 and a loadmodulator 20 and outputs the signal supplied from the encoder 16 to theselected modulator.

The selector 17 selects the modulator 19 or the load modulator 20 underthe control of a controller 21. When a communication mode is the passivemode and the communication apparatus 1 acts as the target, thecontroller 21 makes the selector 17 to select the load modulator 20.Further, when the communication method is the active mode or when theconstruction mode is the passive mode as well as the communicationapparatus 1 acts as the initiator, the controller 21 makes the selector17 to select the modulator 19. Accordingly, in a case in which thecommunication method is the passive mode and the communication apparatus1 acts as the target, the signal output from the encoder 16 is suppliedto the load modulator 20 through the selector 17. In the other cases,however, the signal is supplied to the modulator 19 through the selector17.

An electromagnetic wave output unit 18 flows a current to the antenna 11to cause the antenna 11 to radiate (the electromagnetic wave) of acarrier wave having a predetermined single frequency. The modulator 19modulates the carrier wave as the current, which is flown in the antenna11 by the electromagnetic wave output unit 18, according to the signalsupplied from the selector 17. With this operation, the antenna 11radiates an electromagnetic wave obtained by modulating the carrier waveaccording to the data output from the data processor 15 to the encoder16.

The load modulator 20 changes impedance when the coil as the antenna 11is observed from the outside according to the signal supplied from theselector 17. When an RF field (magnetic field) is formed in the vicinityof the antenna 11 by an electromagnetic wave output by other apparatusas a carrier wave, the RF field in the vicinity of the antenna 11 alsochanges as the impedance when the coil as the antenna 11 is observedchanges. With this arrangement, the carrier wave as the electromagneticwave output from the other apparatus is modulated according to thesignal supplied from the selector 17, thereby the data output from thedata processor 15 to the encoder 16 is transmitted to the otherapparatus that outputs the electromagnetic wave.

Here, amplitude modulation (ASK (Amplitude Shift Keying)), for example,can be employed as a modulation system in the modulator 19 and the loadmodulator 20. However, the modulation system in the modulator 19 and theload modulator 20 is not limited to ASK, and Phase Shift Keying (PSK),Quadrature Amplitude Modulation (QAM), and the like can be alsoemployed. Further, a degree of modulation of amplitude is not limited tothe values from 8% to 30%, 50%, 100% and the like, and an appropriatevalue may be selected.

The controller 21 controls the respective blocks constituting thecommunication apparatus 1. A power supply 22 supplies necessary power tothe respective blocks constituting the communication apparatus 1. Notethat, in FIG. 4, lines showing that the controller 21 controls therespective blocks constituting the communication apparatus 1 and linesshowing that the power supply 22 supplies power to the respective blocksconstituting the communication apparatus 1 are omitted to prevent thefigure from being made complex.

In the case described above, the decoder 14 and the encoder 16 processesManchester Code. However, it is possible for the decoder 14 and theencoder 16 to select and process one of a plurality of types of codessuch as a modified mirror code, NRZ, and the like, in addition toManchester Code.

Further, when the communication apparatus 1 operates only as the targetof the passive mode, the communication apparatus 1 can be arrangedwithout providing the selector 17, electromagnetic wave output unit 18,and the modulator 19. Further, in this case, the power supply 22 obtainspower from, for example, an external electromagnetic wave received bythe antenna 11.

As described above, the communication apparatuses 1, 2, and 3 arearranged such that they can execute communications by a plurality ofcommunication protocols, and a communication executed by the arrangementof FIG. 4 using NFC is one of the communications executed by theplurality of communication protocols. As the plurality of communicationprotocols, there can be employed, for example, InternationalOrganization for Standardization/International ElectrotechnicalCommission (ISO/IEC) 14443 that regulates a communication by an IC card,ISO/IEC 15693 that regulates a communication of Radio Frequency Tag (RFtag), Bluetooth, and further WLAN, and other communication protocols, inaddition to the NFC.

FIG. 5 shows a corresponding relation between the communicationprotocols of the communication apparatuses 1 to 3 and an OSI hierarchymodel.

In the communication apparatuses 1, 2, and 3, for example, InternetApplications (for example, Hyper Text Transfer Protocol (HTTP), FileTransfer Protocol (FTP), and the like), and other arbitrary applicationscan be employed to seventh Application Layer as an uppermost layer,sixth Presentation Layer, and a fifth Session Layer.

Transmission Control Protocol (TCP), User Datagram Protocol (UDP), andthe like, for example, can be employed to fourth Transport Layer.

Internet Protocol (IP) and the like, for example, can be employed tothird Network Layer.

Second Data Link Layer can be divided into upper Logical Link ControlLayer (LLC layer) and lower Media Access Control Layer (MAC layer).

In the communication apparatuses 1, 2, and 3, Near Field CommunicationInterface and Protocol Data Link (NFCIP-DL) is employed to the LLClayer. Here, NFCIP-DL is a communication protocol of a part of NFC andcan be controlled from the upper layer thereof through Service AccessPoint (SAP). In NFCIP-DL, the information of a communication protocolthat can be used by a communication opponent (hereinafter, appropriatelycalled available protocol information) is obtained through NFCIP-1 to bedescribed later. Further, NFCIP-DL exchanges information (hereinafter,appropriately called communication information), which is necessary toexecute a communication by a communication protocol of MAC layer (andfurther a physical layer) switched from NFCIP-1 therethrough in responseto a request from the upper layer, between it and a communicationapparatus that executes a communication by NFCIP-1. Then, NFCIP-DLswitches (handovers) the communication protocol from NFCIP-1 to acommunication protocol corresponding to the exchanged communicationinformation in response to the request from the upper layer. Note thatthe communication protocol switched from NFCIP-1 is selected fromavailable communication protocols represented by the available protocolinformation.

As described above, when NFCIP-DL is mounted on the communicationapparatuses 1, 2, and 3, the apparatuses can switch (handover) thecommunication protocol of MAC layer (and further the physical layer).

NFCIP-1, ISO/IEC 14443-2, ISO/IEC 14443-3, and ISO/IEC 14443-4 employedto the IC card, ISO/IEC 15693-2 employed to the RF tag, Bluetooth, andfurther WLAN and other protocols, for example, can be employed to MAClayer. Note that it is assumed in the embodiment that a plurality ofcommunication protocols including NFCIP-1 are employed to the MAC layerin, for example, the communication apparatuses 1, 2, and 3.

Here, NFCIP-1 is a communication protocol of a part of NFC and detectswhether or not an RF field exists in the vicinity, and when no RF fieldis detected, NFCIP-1 outputs an electromagnetic wave (forms the RF fieldby itself). Further, when a communication opponent exists in the RFfield, that is, when NFCIP-1 is brought into vicinity of thecommunication opponent, NFCIP-1 obtains Identification (ID) composed ofrandom numbers from the communication opponent and communicates with thecommunication opponent by specifying it by ID. That is, according toNFCIP-1, when a plurality of apparatuses exist in the vicinity of it, auser can specify an apparatus acting as a communication protocol fromthe plurality of apparatuses and communicates with the apparatus withoutexecuting an operation for selecting the apparatus acting as thecommunication opponent from the plurality of the apparatus.

Specifically, in, for example, WLAN composed of a plurality ofcomputers, when one computer transmits and receives data to and from theother one computer, the other one computer must be specified by a userin such as manner that the user selects the icon representing the otherone computer, to and from which the data is transmitted and received,from a plurality of icons displayed on a screen to represent theplurality of computers constituting WLAN. In this case, when WLAN iscomposed of many computers, it is burdensome for the user to search theicon representing the other one computer.

In contrast, in NFCIP-1, when it is located in the vicinity of acommunication opponent, it obtains ID, which is composed of randomnumbers, of the communication opponent and communicates with thecommunication opponent by specifying it by ID. Therefore, according toNFCIP-1, since the user can execute a communication by specifying acommunication opponent only by, for example, causing the communicationapparatus 1 (2 or 3) to approach over an apparatus which he or shedesires to select as a communication opponent, the user need not executethe burdensome job as described above.

A device and the like, which are necessary to a communication executedby a communication protocol employed in MAC layer by the communicationapparatuses 1 to 3, are employed to the first physical layer. That is,in NFCIP-1, ISO/IEC 22050, for example, which regulates devicesdedicated for a communication by NFC (NFC Devices) and Cartridge MemoryDevice, can be employed to the physical layer. In ISO/IEC 14443-2,ISO/IEC 14443-3, and ISO/IEC 14443-4, for example, ISO/IEC 14443, whichregulates compatible IC Cards, can be employed to the physical layer. InISO/IEC 15693-2, a device dedicated to a communication by the RF tag canbe employed to the physical layer. Further, in Bluetooth, devicesdedicated to a communication by Bluetooth (Bluetooth devices) can beemployed to the physical layer. Further, in the communication protocolof MAC layer of WLAN and the like, other devices dedicated to acommunication by the communication protocol can be employed to thephysical layer.

Next, FIG. 6 shows a format of data transmitted and received to and fromNFCIP-DL as a part of the NFC.

In NFCIP-DL, the data is transmitted and received in a unit calledProtocol data Unit (NFCIP-DL PDU).

NFCIP-DL PDU has the same format as a packet transmitted and received inPoint to Point Protocol (PPP), thereby affinity can be improved betweenNFCIP-DL and PPP.

NFCIP-DL PDU has Start Mark, Address, Control, Protocol, NFCIP-DLheader, Data, CRC, and End Mark sequentially disposed from the leadingend thereof.

Start Mark has, for example, 1 byte of 7Eh (h shows that a value infront of it is a hexadecimal numeral) disposed therein as a start markshowing the start of NFCIP DL PDU. Address has, for example, 1 byte ofFFh disposed therein as predetermined data. Control also has, forexample, 1 byte of 03h disposed therein as predetermined data.

In NFCIP-DL, the data disposed in Start Mark, Address, and Control isthe same as that in PPP.

Protocol has, for example, 2 bytes of 0001h disposed therein. When 0001his disposed in Protocol in PPP, it is assumed that the data disposed inData has no particular meaning. However, when 0001h is disposed inProtocol in NFCIP-DL, the packet (PDU) is handled as NFCIP-DL PDU.

NFCIP-DL header has 6-bytes of header information disposed therein whichwill be explained below with reference to FIG. 7. Data has necessarydata disposed therein. CRC has Cyclic Redundancy Checking (CRC) codedisposed therein which is determined for Address, Control, Protocol,NFCIP-DL header, and Data.

End Mark has, for example, 1 byte of 7Eh as an end mark showing the endof NFCIP-DL PDU. The end mark is the same as that in PPP.

FIG. 7 shows a format of the header information disposed in NFCIP-DLheader.

The header information is composed of 6 bytes as described above. Codes4Eh, 46 h, and 43 h, which show the characters N, F, C of NFC, aredisposed in Byte 1, Byte 2, and Byte 3 from the leading end of theheader information. A value showing the version of NFC is disposed inByte 4. Note that, in FIG. 7, the value showing the version of NFC is21h.

Byte 5 is Reserved for Future Use (RFU) and has 00h disposed therein inFIG. 7.

Byte 6 has Directive Code disposed therein which shows various types ofrequests and responses to them. That is, as explained in FIG. 4, in NFC,a communication is executed between the initiator and the target in sucha manner that the initiator transmits a request and the target returns aresponse to the request. Directive Code as a code showing the requestand the response is disposed in the sixth byte.

As described above, in NFCIP-DL, available protocol information as theinformation of a communication protocol that can be used by acommunication opponent is obtained, and communication information, whichis necessary to execute a communication by a certain communicationprotocol included in the available communication protocols representedby the available protocol information, is exchanged. Then, NFCIP-DLswitches (handovers) the communication protocol from NFCIP-1 to acommunication protocol corresponding to the exchanged communicationinformation.

AVAILABLE_MEDIA Request is transmitted from the initiator to the targetto request the available protocol information. AVAILABLE_MEDIA Requestis transmitted from the initiator to the target to request the availableprotocol information. AVAILABLE_MEDIA Response is transmitted from thetarget to the initiator as a response to AVAILABLE_MEDIA Request.

Further, MEDIA_HANDOVER Request is transmitted from the initiator to thetarget to request to switch (handover) a communication protocol.MEDIA_HANDOVER Response is transmitted from the target to the initiatoras a response to MEDIA_HANDOVER Request.

In AVAILABLE_MEDIA Response, a directive code is set to, for example,22h. Further, when the information of all the communication protocolsthat can be used by the communication opponent (here, target) isrequested, 01h is disposed to Data.

Further, when usability of a particular communication protocol isrequested to the communication opponent in AVAILABLE_MEDIA Response,information showing the particular communication protocol is disposed toData.

More specifically, FIG. 8 shows a format of Data of NFCIP-DL PDU whenthe usability of the particular communication protocol is requested tothe communication opponent in AVAILABLE_MEDIA Request.

Length of PDU Data (n), which shows the data length of Data, is disposedto the leading end of Data. Media Pack Count, which shows the number ofMedia Parameter Packs to be described later, is disposed behind the datalength. Then, Media Parameter Packs as many as the number shown by MediaPack Count are disposed behind Media Pack Count.

Media Parameter Pack is composed of Media Code and Attribute disposed inthis order. One byte of media code showing the communication protocol isdisposed to Media Code, and information as to the communication protocolrepresented by a media code disposed to Media Code is disposed toAttribute.

In AVAILABLE_MEDIA Response, when, for example, availability of twocommunication protocols, that is, Institute of Electrical andElectronics Engineers (IEEE) 802.11 that regulates WLAN and Bluetoothare requested to the communication opponent, two Media Parameter Packs,that is, Media Parameter Pack, in which a media code representing IEEE802.11 is disposed, and Media Parameter Pack, in which a media coderepresenting Bluetooth is disposed, are disposed behind Media PackCount.

In AVAILABLE_MEDIA Response as the response to AVAILABLE_MEDIA Request,the directive code is set to, for example, 23h. Further, inAVAILABLE_MEDIA Response, information showing a communication protocolthat can be used by an apparatus (here, the target as an apparatus thatreceives AVAILABLE_MEDIA Request) is disposed in Data.

More specifically, FIG. 9 shows a format of Data of NFCIP-DL PDU asAVAILABLE_MEDIA Response.

Length of PDU Data (n) is disposed to the leading end of Data likewisethe case shown in FIG. 8. Further, Current Phase, Status, and Error Codeare sequentially disposed behind Length of PDU Data (n). Here, CurrentPhase shows that NFCIP-DL PDU belongs to any of the phases of NFCIP-DLdescribed later. Status shows the present state (status) of NFCIP-DLPDU, and Error Code shows a code corresponding to an error that occursin any processing.

Media Pack Count is disposed behind Error Code. Media Pack Count showsthe number of Media Parameter Packs disposed behind it.

Media Parameter Packs as many as the number shown by Media Pack Countare disposed behind Media Pack Count to show each communication protocolthat can be used by NFCIP-DL PDU. Note that since the arrangement ofMedia Parameter Pack in FIG. 9 is the same as that described in FIG. 8,the explanation thereof is omitted.

The initiator, which has transmitted AVAILABLE_MEDIA Request, receivesAVAILABLE_MEDIA Response transmitted by the target in response toAVAILABLE_MEDIA Request and recognizes a communication protocol that canbe used by the target referring to Media Parameter Pack inAVAILABLE_MEDIA Response.

Note that when 01h is set to Data of AVAILABLE_MEDIA Request from theinitiator, the target transmits AVAILABLE_MEDIA Response, which hasMedia Parameter Pack as to all the communication protocols that can beused by it, to the initiator. Further, Data of AVAILABLE_MEDIA Requestfrom the initiator is as shown in FIG. 8, the target transmitsAVAILABLE_MEDIA Response, which has information whether or not it canuse the respective communication protocols corresponding to MediaParameter Pack of AVAILABLE_MEDIA request, to the initiator.

In MEDIA_HANDOVER Request, the directive code is set to, for example,24h. Further, information of a communication protocol handovered fromNFCIP-1 is disposed to Data.

More specifically, FIG. 10 shows a format of Data of NFCIP-DL PDU asMEDIA_HANDOVER Request.

Length of PDU Data (lln), which shows the data length of Data, isdisposed to the leading end of Data. Media Parameter Pack as to acommunication protocol handovered from NFCIP-1 is disposed behind thedata length. Note that since the arrangement of the Media Parameter Packin FIG. 10 is the same as that described in FIG. 8, the explanationthereof is omitted.

In MEDIA_HANDOVER Response as the response to MEDIA_HANDOVER Request,the directive code is set to, for example, 25h. Further, predetermineddata is disposed to DATA in MEDIA_HANDOVER Response.

More specifically, FIG. 11 shows a format of Data of NFCIP-DL PDU asMEDIA_HANDOVER Response.

Length of PDU Data (04h), Current Phase, Status, and Error Code aresequentially disposed to Data from the leading end thereof. Since Lengthof PDU Data, Current Phase, Status, and Error Code are the same as thoseexplained in FIG. 9, the explanation thereof is omitted.

AVAILABLE_MEDIA Request and AVAILABLE_MEDIA Response are transmittedbetween the initiator and the target by NFCIP-1, thereby the initiatorrecognizes a communication protocol that can be used by the target.Further, MEDIA_HANDOVER Request and MEDIA_HANDOVER Response aretransmitted between the initiator and the target by NFCIP-1, thereby theinitiator and the target handovers from a communication by NFCIP-1 to acommunication by a certain communication protocol recognized by theinitiator. Thereafter, the initiator and the target execute acommunication by the communication protocol after the handover.

Next, a communication phase by NFCIP-DL will be explained with referenceto FIG. 12.

A communication by NFCIP-DL has six phases, that is, Idling phase P1,Link establishment-waiting phase P2, Link establishment phase P3,Authentication phase P4, Network layer protocol phase P5, and Linktermination phase P6.

In the communication by NFCIP-DL, first, a process goes to Idling phaseP1 as an initial phase. In Idling phase P1, detection of the RF fielddescribed above and the like are executed.

In Idling phase P1, when it is requested, for example, to detect anapparatus that can make an NFC communication, the process goes to Linkestablishment-waiting phase P2, in which the apparatus that can make theNFC communication begins to be searched. Note that the process may go toIdling phase P1, Link establishment phase P3, or Link termination phaseP6 from Link establishment-waiting phase P2.

When, for example, the apparatus that can make the NFC communication isdetected in Link establishment-waiting phase P2, the process goes toLink establishment phase P3. In Link establishment phase P3, ID composedof a random number (hereinafter, appropriately referred to as NFC ID) isrecognized in Link establishment phase P3 to recognize an apparatus as acommunication opponent of the NFC communication, and a link isestablished to the communication opponent whose NFC ID is recognized.Note that the process may go to Idling phase P1, Authentication phaseP4, or Link termination phase P6 from Link establishment phase P3.

When the link is established to the communication protocol whose NFC IDis recognized, the process goes to Authentication phase P4. InAuthentication phase P4, mutual authentication is executed between theapparatus and the communication opponent whose NFC ID recognized. Notethat the process may go to Idling phase P1, Network layer protocol phasePS, or Link termination phase P6 from Authentication phase P4. Further,Link termination phase P6 may be skipped.

When, for example, the mutual authentication is succeeded between theapparatus and, for example, the communication opponent whose NFC ID isrecognized in Authentication phase P4, the process goes to Network layerprotocol phase P5. In Network layer protocol phase P5, necessary data isexchanged (transmitted) bet the apparatus and the communication opponentwhose NFC ID is recognized. Note that the process may go to Idling phaseP1 or Link termination phase P6 from Network layer protocol phase P5.

In Network layer protocol phase PS, when, for example, it is requestedto terminate the NFC communication, the process goes to Link terminationphase P6. In Link termination phase P6, the link to the communicationopponent whose NFC ID is recognized is interrupted, and the process goesto Idling phase P1.

Next, processing between the initiator and the target will be explainedwith respect to FIGS. 13 and 14 when an NFCIP-1 communication is startedbetween the initiator and the target and thereafter the communicationprotocol of MAC Layer (and further Physical layer) is handovered fromNFCIP-1 to other communication protocol.

First, processing executed by the initiator will be explained.

First, the initiator is placed in an idle state at step S1.

Thereafter, the initiator goes from step Si to step S2, at which theinitiator forms the RF field and executes polling for requesting NFC ID,and then the initiator goes to step S3. At step S3, the initiatordetermines whether or not there is a response to the polling from thetarget. When it is determined at step S3 that there is no response tothe polling at step 53, the initiator returns to step S2 and repeats thesame processing thereafter.

Further, when it is determined at step S3 that there is the response tothe polling, the initiator goes to step S4 at which it requests NFC IDto the target from which the response is returned and receives NFC IDtransmitted from the target in response to the request. The initiatorspecifies the target as the communication opponent by NFC ID.

Thereafter, the initiator goes from step S4 to step S5 at which itexecutes mutual authentication between it and the target recognized asthe communication opponent, further exchanges a transaction ID and atransaction key therebetween, and the initiator goes to step S6. Notethat after the transaction ID and the transaction key are exchanged, theinitiator and the target encrypt data, which is transmitted therebetweenthereafter, using the transaction ID and the transaction key as acryptographic key.

At step S6, the initiator requests the target a communication protocolthat can be used by the target and receives the available protocolinformation of the available communication protocol transmitted from thetarget in response to the request. That is, at step S6, the initiatortransmits AVAILABLE_MEDIA Request to the target and receivesAVAILABLE_MEDIA Response as a response to AVAILABLE_MEDIA Request fromthe target. With this operation, the initiator recognizes the availablecommunication protocol of the target.

Thereafter, the initiator selects a desired communication protocol(hereinafter, appropriately referred to as desired protocol) from thecommunication protocols that can be used by the initiator and the targetand goes from step S6 to 57. At step S7, the initiator exchangescommunication information, which is necessary to a communication by thedesired protocol, between it and the target and goes to step S8.

At step S8, the initiator switches (handovers) the communicationprotocol of MAC Layer (and further Physical Layer) from NFCIP-1 to thedesired protocol. That is, at step S8, the initiator transmitsMEDIA_HANDOVER Request to the target and receives AVAILABLE_MEDIAResponse as a response to MEDIA_HANDOVER Request from the target. Then,the initiator switches the communication protocol of MAC Layer (andfurther Physical Layer) from NFCIP-1 to the desired protocol.

Thereafter, the initiator goes from step S8 to S9 at which it terminatesthe NFC communication. After the termination of the NFC communication,the initiator makes a communication by the desired protocol based on thecommunication information obtained at step S7 and returns to step Siafter the termination of the communication.

Next, processing executed by the target will be explained with referenceto a flowchart of FIG. 14.

First, the target is placed in an idle state at step S21.

Thereafter, when, for example, the target receives polling from theinitiator, it goes from step S21 to S22 at which it transmits a responseto the polling to the initiator and goes to step S23. At step S23, theinitiator waits for a request for an NFC ID from the initiator, createsNFC ID by a random number, transmits it to the initiator, and goes tostep S24. Here, for example, the request for the NFC ID from theinitiator includes the NFC ID of the initiator, and the target specifiesthe initiator acting as a communication opponent by the NFC ID of theinitiator.

Thereafter, the target goes from step S23 to step S24 at which itexecutes mutual authentication between it and the initiator specified asthe communication opponent by the NFC ID and further exchanges atransaction ID and a transaction key between it at the time of mutualauthentication and goes to step S25. Note that, as explained in FIG. 13,after the transaction ID and the transaction key are exchanged, thetarget and the initiator encrypt data, which is transmitted therebetweenthereafter, using the transaction ID and the transaction key as acryptographic key.

At step S25, the target waits for transmission of a request for anavailable communication protocol from the initiator and transmits theavailable protocol information of a communication protocol, which can beused by the target, to the initiator. That is, at step S25, the targetreceives AVAILABLE_MEDIA Request from the initiator and transmitsAVAILABLE_MEDIA Response as a response to AVAILABLE_MEDIA Request to theinitiator as available protocol information.

Thereafter, the target goes from step S25 to S26 at which it exchangescommunication information, which is necessary to the communication bythe desired protocol explained in FIG. 13, between it and the initiatorand goes to step S27.

At step S27, the target switches (handovers) the communication protocolof MAC Layer (and further Physical Layer) from NFCIP-1 to the desiredprotocol. That is, at step S27, the target receives MEDIA_HANDOVERRequest from the initiator and transmits MEDIA_HANDOVER Response as aresponse to MEDIA_HANDOVER Request to the initiator. Then, the targetswitches the communication protocol of MAC Layer (and further PhysicalLayer) from NFCIP-1 to the desired protocol.

Thereafter, the target goes from step S27 to S28 at which it terminatesthe NFC communication. After the termination of the NFC communication,the target makes a communication by the desired protocol based on thecommunication information obtained at step S26 and returns to step S21after the termination of the communication.

Next, when it is assumed, for example, that the communicationapparatuses 1 and 2 can make both of a communication by NFC and acommunication (BT communication) by Bluetooth, processing will beexplained which is executed by the communication apparatuses 1 and 2 toexecute the NFC communication first and then to handover the NFCcommunication to the BT communication.

Note that FIG. 15 shows an example of functional arrangements of thecommunication apparatuses 1 and 2.

More specifically, in FIG. 15, the communication apparatus 1 has an NFCcommunication unit 51 and a BT communication unit 52, and thecommunication apparatus 2 has an NFC communication unit 61 and a BTcommunication unit 62. The NFC communication units 51 and 62 execute theNFC communication, and the BT communication units 52 and 62 execute theBT communication.

FIG. 16 is a flowchart explaining processing executed by thecommunication apparatuses 1 and 2 when the NFC communication is executedfirst using the communication apparatuses 1 and 2 as the initiator andthe target, and thereafter the NFC communication is handovered to the BTcommunication.

First, the NFC communication unit 51 as the initiator executes pollingat step S51, and NFC communication unit 61 as the target receives thepolling at step S52 and transmits a response to the polling to the NFCcommunication unit 51 at step S52.

When the response to the polling is transmitted from the NFCcommunication unit 61, the NFC communication unit 51 receives theresponse and requests an NFC ID to the NFC communication unit 61. TheNFC communication unit 61 receives the request for the NFC ID from theNFC communication unit 51 and transmits the NFC ID thereof to the NFCcommunication unit 51 in response to the request. The NFC communicationunit 51 receives the NFC ID from the NFC communication unit 61 andspecifies the NFC communication unit 61 (communication apparatus 2) as acommunication opponent by the NFC ID. Note that the request for the NFCID transmitted from the NFC communication unit 51 to the NFCcommunication unit 61 includes the NFC ID of the NFC communication unit51, and the NFC communication unit 61 specifies the NFC communicationunit 51 (communication apparatus 1) as a communication opponent by theNFC ID.

Thereafter, mutual authentication is executed between the NFCcommunication units 51 and 61 by transmitting data for mutualauthentication therebetween at step S55, and further a transaction IDand a transaction key are exchanged at the time. Thereafter, data istransmitted between the NFC communication units 51 and 61 after it isencrypted using the transaction ID and the transaction key as acryptographic key. Note that the mutual authentication may be skipped(may not be executed) as described above.

When the mutual authentication is succeeded at step S55, the NFCcommunication unit 51 goes to step S56 at which it transmits a requestfor available protocol information that is can be used by thecommunication apparatus 2 (AVAILABLE_MEDIA Request) to the NFCcommunication unit 61, and the NFC communication unit 61 receives therequest. At step S57, the NFC communication unit 61 transmits theavailable protocol information that can be used by the communicationapparatus 2 (AVAILABLE_MEDIA Response) to the NFC communication unit 51,and the NFC communication unit 51 receives the available protocolinformation.

In this case, the NFC communication unit 51 recognizes that thecommunication apparatus 2 can execute the BT communication from theavailable protocol information received from the NFC communication unit61.

It is assumed that the communication apparatus 1 determines to switchthe NFC communication to the BT communication because the transmissionrate of the BT communication is higher than that of the NFCcommunication and thus the BT communication is more advantageous thanthe NFC communication to transmit a large amount of data between thecommunication apparatuses 1 and 2.

In this case, at step S58, communication information necessary to the BTcommunication is exchanged between the NFC communication units 51 and61. The communication information necessary to the BT communicationincludes, for example, Bluetooth Device (BD) address for specifying acommunication opponent in the BT communication. That is, the BTcommunication unit 52 of the communication apparatus 1 and the BTcommunication unit 62 of the communication apparatus 2 have unique BDaddresses, respectively, and the BD address of the BT communication unit52 is transmitted from the NFC communication unit 51 to the NFCcommunication unit 61, and the NFC communication unit 61 receives the BDaddress at step S58. Further, at step S58, the BD address of the BTcommunication unit 62 is transmitted from the NFC communication unit 61to the NFC communication unit 51, and the NFC communication unit 51receives the BD address.

Thereafter, the NFC communication unit 51 transmits a request forswitching the NFC communication to the BT communication (MEDIA_HANDOVERRequest) to the NFC communication unit 61, and the NFC communicationunit 61 receives the switching request at step S59. Then, the BTcommunication unit 52 transmits a response (MEDIA_HANDOVER Response) tothe switching request from the NFC communication unit 51, and the NFCcommunication unit 51 receives the response at step S60.

Thereafter, the communication apparatus 1 switches (handovers) the NFCcommunication executed by the NFC communication unit 51 to the BTcommunication executed by the BT communication unit 52 at step S61.Further, the communication apparatus 2 also switches (handovers) the NFCcommunication executed by the NFC communication unit 61 to the BTcommunication executed by the BT communication unit 62 at step S62.

The NFC communication units 51 and 61 terminate the NFC communication atstep S63. Thereafter, at step S64, the BT communication is executedbetween the BT communication units 52 and 62 based on the communicationinformation exchanged at step S58.

That is, the BT communication unit 52 executes the BT communication byspecifying the BT communication unit 62 as a communication opponent bythe BD address of the BT communication unit 62 received by the NFCcommunication unit 51 at step S58. Likewise, the BT communication unit62 also execute the BT communication by specifying the BT communicationunit 52 as a communication opponent by the BD address of the BTcommunication unit 52 received by the NFC communication unit 61 at stepS58.

Accordingly, in this case, the BT communication units 52 and 62 canexecute the BT communication by specifying the communication opponentswithout the designation of the communication opponents executed by auser.

More specifically, when there are many BT devices capable of executingthe BT communication, the respective BT devices transmits informationbetween them and the other BT devices and collect information as to theother BT devices. In the respective BT devices, icons showing the otherBT devices are displayed on screens based on the collected information.In this case, when the user intends to transmit data from one BT device#1 of the many BT devices to other one BT device #2, the user mustdesignate the BT device #2 as a communication opponent to which the datais transmitted by searching the icon of the BT device #2 from the iconsof the many BT devices displayed on the screen of the BT device #1 andmanipulating the icon.

In contrast, according to the communication system of FIG. 1, when thereexist many communication apparatuses similar to the communicationapparatuses 1 to 3, even if it is intended to transmit data from thecommunication apparatus 1 to the communication apparatus 2, the data canbe transmitted from the communication apparatus 1 to the communicationapparatus 2 only by approaching the communication apparatus 1 to thecommunication apparatus 2.

More specifically, in the communication apparatuses 1 and 2, when theyapproach each other, it is recognized that the communication apparatuses1 and 2 make the BT communication by the NFC communication, and a BDaddress and the like as information necessary to the BT communicationare exchanged between the communication apparatuses 1 and 2. Further, inthe communication apparatuses 1 and 2, the NFC communication is switched(handovered) to the BT communication, and the BT communication isexecuted by specifying the communication opponent based on the BDaddress.

Accordingly, the user can acquire the advantages of both the NFCcommunication and the BT communication.

More specifically, when, for example, the transmission rate of the BTcommunication is higher than that of the NFC communication, the useronly approaches the communication apparatuses 1 and 2 each other andneed not execute a job for specifying other communication opponent andfurther can transmit data at high speed by BT communication.

Next, a series of the processings described above may be executed bydedicated hardware or may be executed by software. When the series ofprocessings is executed by the software, a program constituting thesoftware is installed on a general-purpose computer, a microcomputer,and the like.

FIG. 17 shows an example of an arrangement of a computer on which aprogram for executing the series of processings is installed.

The program can be previously recorded in a hard disc 105 and a ROM 103as a recording medium built in the computer.

Otherwise, the program may be temporarily or permanently stored(recorded) in a removable recording medium ill such as a flexible disc,compact disc read only memory (CD-ROM), magneto optical (MO) disc,digital versatile disc (DVD), magnetic disc, semiconductor memory, andthe like. The removable recording medium 111 as described above can beprovided as so-called package software.

It should be noted that the program may be transmitted from a downloadsite to the computer by wireless through a digital broadcastingartificial satellite or to the computer through a fixed-line networksuch as Local Area Network (LAN), the Internet, and the like, and thecomputer may receive the thus transferred program by a transmission unit108 and install it on the hard disc 105 built therein, in addition tothat the program is installed on the computer from the removablerecording medium ill as described above.

The computer has a central processing unit (CPU) 102 built therein. Aninput/output interface 110 is connected to the CPU 102 through a bus101, and when a command is input to the CPU 102 through the input/outputinterface 110 by a user who manipulates an input unit 107 composed of akeyboard, mouse, microphone, and the like, the CPU 102 executes theprogram stored in the read only memory (ROM) 103. Otherwise, the CPU 102loads the program, which is stored in the hard disc 105, the program,which is transferred from the satellite or the network, received by thetransmission unit 108, and installed to the hard disc 105, or theprogram, which is read out from the removable recording medium 111mounted on a drive 109 and installed to the hard disc 105, to a randomaccess memory (RAM) 104 and executes it. With the above operation, theCPU 102 executes processing according to the flowchart described aboveor processing according to the arrangement of the block diagram. Then,the CPU 102 outputs a result of the processing from an output unit 106composed of a speaker and the like through the input/output interface110 or transmits it from the transmission unit 108 and further recordsit to the hard disc 105.

In the specification, a processing step for describing the program forcausing the computer to execute various types of processings need notalways be processed in time series according to a sequence described inthe flowchart and includes processings executed in parallel orindividually (for example, parallel processings or processings executedby an object).

Further, the program may be processed by a single computer or may beprocessed discretely by a plurality of computers.

Note that, the embodiment is applied to a wireless communication, butmay be also applied to a cable communication and to a mixedcommunication of the wireless communication and the cable communication.

Further, although the NFC communication is switched to a communicationby other communication protocol in the embodiment, it is also possibleto switch a communication by an arbitrary communication protocol to acommunication by other arbitrary communication protocol, that is, toswitch, for example, ISO/IEC 14443-3 to Bluetooth, and the like.

Further, although the NFC communication is switched to the BTcommunication in the embodiment, it is also possible to further switchthe BT communication to a communication by another communicationprotocol thereafter.

As described above, according to the embodiments, there can be executeda communication which can acquire the advantages of a plurality ofcommunication protocols.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

The application is claimed as follows:
 1. A communication apparatuscomprising: a carrier wave generator configured to generate a firstelectromagnetic wave; a modulator configured to modulate the firstelectromagnetic wave for transmitting a first message to a firstcommunication device; a load modulator configured to modulate a secondelectromagnetic wave generated by the first communication device fortransmitting a second message to the first communication device; acontroller configured to control the communication apparatus to:transmit the first message when the second electromagnetic wave is notdetected and, transmit the second message when the secondelectromagnetic wave is detected.
 2. The communication apparatusaccording to claim 1, wherein the controller is configured to controlthe carrier wave generator not to generate the first electromagneticwave when the second electromagnetic wave is detected.
 3. Thecommunication apparatus according to claim 2, wherein the first messageincludes a first inquiry for identification information of the firstcommunication device.
 4. The communication apparatus according to claim3, wherein the communication apparatus is configured to receive a firstresponse associated with the first inquiry, and wherein the firstresponse includes a first random number.
 5. The communication apparatusaccording to claim 2, wherein the second message includes a secondresponse associated with a second inquiry for identification informationof the communication apparatus, and wherein the communication apparatusis configured to receive the second inquiry from the first communicationdevice.
 6. The communication apparatus according to claim 5, wherein thesecond response includes a second random number.
 7. The communicationapparatus according to claim 1, wherein the communication apparatus isconfigured to perform a near field communication with the firstcommunication device when the first communication device is near thecommunication apparatus.
 8. The communication apparatus according toclaim 1, wherein a transmission rate of the communication apparatus islower than the first communication device.
 9. The communicationapparatus according to claim 1, wherein the communication apparatus isfurther configured to receive protocol information indicative of acommunication protocol which is available by the first communicationdevice.
 10. A communication method for a communication apparatus, thecommunication method comprising: generating a first electromagnetic waveby a carrier wave generator; modulating the first electromagnetic wavefor transmitting a first message to a first communication device by amodulator; modulating, by a load modulator, a second electromagneticwave generated by the first communication device for transmitting asecond message to the first communication device; transmitting the firstmessage when the second electromagnetic wave is not detected; andtransmitting the second message when the second electromagnetic wave isdetected.
 11. The communication method according to claim 10, furthercomprising controlling the carrier wave generator not to generate thefirst electromagnetic wave when the second electromagnetic wave isdetected.
 12. The communication method according to claim 11, whereinthe first message includes a first inquiry for identificationinformation of the first communication device.
 13. The communicationmethod according to claim 12, further comprising receiving a firstresponse associated with the first inquiry, wherein the first responseincludes a first random number.
 14. The communication method accordingto claim 11, wherein the second message includes a second responseassociated with a second inquiry for identification information of thecommunication apparatus, wherein the second inquiry is received from thefirst communication device.
 15. The communication method according toclaim 14, wherein the second response includes a second random number.16. The communication method according to claim 10, further comprisingperforming a near field communication with the first communicationdevice when the first communication device is near the communicationapparatus.
 17. The communication method according to claim 10, wherein atransmission rate of the communication apparatus is lower than the firstcommunication device.
 18. The communication method according to claim10, further comprising receiving protocol information indicative of acommunication protocol which is available by the first communicationdevice.